Valmet’s long experience in the papermaking industry and broad process expertise help you to choose the right roll cover for each board and paper making application. Our roll covers and coatings are based on state-of-the-art polymer and thermal coating technologies that provide excellent wear resistance, stable roughness and hardness, and durability in demanding operating environments, enabling trouble-free run periods.
Modern board or papermaking lines include hundreds of rolls operating in diﬀerent positions. Each position has its own operating environment, which the rolls and their covers must meet. The major technical parameters for roll covers to be considered in papermaking applications are abrasive contact, local moisture level, temperature, mechanical load and the chemical environment. Good wet condition solutions may diﬀer markedly from solutions which work best in dry conditions.
Roll cover wear is also an important issue to be considered in developing covers for diﬀerent applications. Development at Valmet is based on longstanding know-how in material testing in the laboratory, as well as experience of real life applications. Depending on roll position and cover type – hard ceramic or soft polyurethane, for example – the cover behavior and actual wear phenomena are diﬀerent, and ﬁnding an optimum solution requires speciﬁc know-how and understanding.
Valmet roll covers can be used with iRoll – the most versatile and sensitive online profile measurement tool in the industry. This technology provides real-time insights into the papermaking process, making it possible to adjust and optimize performance to the highest level. Valmet's latest Industrial Internet offering combines process technologies, services and automation to provide applications and services to improve the reliability and performance of your processes. Customers can also have remote monitoring and real-time support from Valmet’s experts through the Performance Centers.
Our global roll workshop network around the world ensures professionals can easily carry out roll cover inspections; perform onsite coating, patching and repair services; and provide application support and general troubleshooting in your location. We also offer support ranging from grinding, recovering, and servicing rolls, to complete roll service management
A major part of the raw materials used in roll covers – polymers, resins and other industrial chemicals – has traditionally been manufactured from fossil-based raw materials, and refined and processed from crude oil. Valmet is now taking a giant leap toward a more holistic approach with a focus on sustainability, aiming to replace as many of the roll cover raw materials as possible with more sustainable alternatives. The target is to use recycled materials and renewable resources, and more broadly to save energy.
Using recycled consumer plastic or glass as the reinforcing fiber or filler in composite roll covers, or bio-based resin and hardener in the polymer matrix, are good examples. What are the benefits of bio-based materials?
“They remove the dependency on crude oil,” states Dr. Jani Turunen from Valmet. He continues: “We only approve renewable materials derived from non-food chain plants or plant parts, meaning their use does not affect global food production. Cultivation and harvesting of plants must not endanger the growth of natural forests either. In the best cases, bio-based materials can be produced from plant parts that would otherwise be waste. Lignin, carbon black made of lignin and nanocellulose are good examples, and all three can be utilized as reinforcing fillers in roll covers.”
Could paper machine roll covers be made of recycled or even bio-based raw materials? After less than two years’ intensive R&D work, Valmet has introduced new composite covers for press, guide and calender rolls representing a new, more sustainable generation of roll cover materials.
The Indian board-maker Vijay Anand has overcome the challenge of traditional rubber covers by upgrading with a Valmet roll cover. Press Roll Cover PP premium polyurethane covers have provided remarkable benefits with an outstanding payback from the investment.